Arc furnace roof



March. 26, 1968 w. GRAY 3,375,315

- ARC FURNACE ROOF Filed Nov. 17, 1964 s Sheets-Sheet 1 INVENTQ A-r-roiauav March 26, 1968 w. GRAY 3,375,315

ARC FURNACE ROOF Filed Nov. 17, 1964 3 Sheets-Sheet Z IMVEMTOE W gym/Mm.

ATTORNEY March 26, 1968 w. GRAY ARC. FURNACE ROOF 3 Sheets-Sheet 3 Filed Nov. 17, 1964 INVENFQE mim I Ar-romusv United States Patent M 3,375,315 ARC FURNACE ROOF William Gray, Uddingston, Scotland, assignor to John G. Stein & Company Limited Filed Nov. 17, 1964, Ser. No. 411,739 Claims priority, application Great Britain, Nov. 18, 1963, 45,410/ 63 Claims. (Cl. 13-9) This invention relates to the construction of furnace roofs and while applicable to furnaces of other kinds, the construction of the invention is particularly suitable for application to the roofs of electric arc furnaces.

Electric arc furnaces have been used for melting steel for very many years, but recently there has been a large increase in the size of individual furnaces. At one time, the normal maximum size of a furnace of this character was ten or fifteen ton capacity, but now furnaces of one hundred ton and even one hundred and twenty ton capacity are coming into operation. The smaller furnaces previously used had roofs of sprung construction, but for larger furnaces it appears desirable to suspend the roofs. This type of construction not only gives better support for the roof, but also helps to prevent so called pinchspalling of the bricks caused by excessive thrust of the hot face of the brick. However, to suspend fully the whole roof of an electric arc furnace in the manner which is common practice in furnaces of other types, such as the open hearth furnace, would be difficult owing to the presence of the electrodes which pass through the roof and the necessity to insulate the hangers in order to avoid induced or eddy currents in the metal suspension system.

In accordance with the present invention, a furnace roof comprising a plurality of suspended bricks is characterised by the fact that a part only of the roof is constituted by the said suspended bricks, which are arranged to form open frames of small size compared to the roof as a whole, and the frames are filled by materials which are supported by the said suspended bricks. This construction not only facilitates the construction of the openings for the electrodes and reduces the problem of in sulating the hangers, which are peculiar to electric furnaces, but also offers numerous other advantages, as will be pointed out below.

One particular constructional form of furnace roof in accordance with the present invention is described below, by way of example only, with reference to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic plan view of the roof;

FIGURES 2 and 3 are diagrammatic views on the lines II--II and TIL-III respectively, of FIGURE 1;

FIGURE 4 is a plan view, on a larger scale, of one frame of the roof; and

FIGURES 5 and 6 are views on the lines V-V and VI-VI respectively, of FIGURE 5.

In the illustrated embodiment of the invention, a roof for an electric furnace some twenty-four feet in diameter comprises suspended bricks arranged to form five main beams M which extend parallel to one another across the roof, with their centre lines some four feet apart. The space between adjacent main beams M (and between the outermost main beams and the curb of the roof) are subdivided by cross beams C disposed at right angles to the main beams M and also formed by suspended bricks. The main and cross beams are so arranged that each of the three electrodes 9 will be disposed approximately centrally in one of the rectangular spaces left between the beams, these spaces or open frames measuring typically some three feet by two and a half feet. The suspended bricks are so shaped that those faces which border the open frames slope inwardly and downwardly, thus allowing the frames to be filled securely with un- 3,375,315 Patented Mar. 26, 1968 suspended brickwork, or with rammed or plastic material.

Each of the main beams M comprises four rows of bricks suspended side by side in pairs. The inner brick I of each pair has parallel vertical side faces, but the outer brick O has its outer side face sloped downwardly and outwardly from the centre line of the beam, so that the beam is of approximately trapezoidal cross section. The cross beams C are formed by two rows of bricks C, suspended in pairs, all these bricks (except those at the extreme ends of the cross beams C) being of the same shape as the bricks O in the outer rows of the main beams M. The bricks at the ends of the cross beams C have (adjacent the side face which slopes downwardly and outwardly) a side face which slopes downwardly and inwardly to mate with the sloping side face of the adjacent main beam. As indicated in FIGURE 2, the curb 1-0 of the roof is faced where necessary with a packing 11 rammed or plastic material to provide an inwardly and downwardly sloping surface which will form an abutment for the fillings of the frames at the periphery of the roof.

The frames through which the electrodes 9 pass are most conveniently filled by a patch 13 of rammed or plastic material and some or all of the remaining boxes may be filled in a similar way. However, it will generally be more convenient to fill them with unsuspended brickwork U, using bricks which taper downwardly in cross section. Such a frame is illustrated in FIGURES 4, 5 and 6.

A roof constructed in the manner described above offers numerous advantages over roofs constructed in accordance with previously known methods. Repair of the roof is much simpler than for a sprung roof, where there is a danger that the whole roof will collapse when a few bricks have worn thin, or fall into the furnace. The new system allows a portion of the roof to be hung with new suspension bricks, which then form a bridge allowing further bricks to be placed to fill the openings. This can be done even when the furnaces are still hot.

The new method of construction largely reduces the number of different brick sizes required to form a roof. Under previous practice fifty or more different shapes may be required to complete a roof, while the new construction described will normally require only four sizes of suspension brick and one, or possibly two, sizes of filler brick. The time taken to build a roof of the new construction is also greatly reduced.

With the new construction the thrusts and stresses of the furnace roof are carried on the suspended bricks forming the beams M and C. These suspended bricks can be made of higher quality than the in-filling bricks, thus effecting economies, while maintaining a balanced roof life.

Constructions in accordance with the invention may be used with bricks made of any material, including silica, high alumina and basic bricks. Bricks of these two latter types are being used to an increasing extent in order to contain the extremely high temperatures required by modern steel making practice, but they are very much heavier than the silica bricks which were previously commonly used. The improved support afforded by constructions in accordance with the present invention renders those constructions particularly suitable for use when the heavier types of brick are employed.

As already indicated, the invention is not limited in its application to the roofs of electric arc furnaces, but may be applied to other types of furnace, such as soaking pits, reheating furnaces and even open hearth furnaces.

What is claimed is:

1. A furnace roof comprising a plurality of spaced parallel main beams extending across the roof, a plurality of cross beams transverse to said main beams, said main beams and said cross beams defining a plurality of rectangular open frames'of'sr'nall size compared to the size ofthe roof as awhole, each of said bearnsbeing comi posed of suspended bricks, and filler materials which fill said open frames, said filler materials being supported by said beams;

2. A furnace. roofaccording to claim 1, whereineach of; said beams comprises at least two rows of suspended bricks arranged sidez-by-side, said bricks having outer faces which slope downwardly and outwardlyv away from the centre line-of said beam so that said beam has a cross section of: approximately trapezoidal form.

, A furnace roof according to claim 1, wherein each of said main beams comprises four rows of suspended bricks arranged side-by-side, two inner rows and two outer rows, saidbricks ofeachof said inner rows having parallel vertical side faces extending longitudinally of said beams,.said bricks of said outer rows having vertical inner faces adjacent said inner rows and having outer faces which slope downwardly and outwardly away from the centre line of the beam, so that said beam increases in width downwardly.

4. A furnace roof according to claim 1, wherein said roof is penetrated by at least one electrode, each electrode passing through one of said open frames, and wherein said filler materials are packed around said electrode between it and the sides of said one frame.

5. A furnace roof according to claim 1, wherein said filler materials in at least some of said frames is constituted by unsuspended' brickwork, including bricks of downwardly tapering cross section.

References. Cited UNITED STATES PATENTS 2,021,424 11/ 1935 McPherson 2637-46 2,029,492 2/1936 Lindner 263 46 2,713,787 7/ 1955 Rose 11'Q99X BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, AssistantExaminer. 

1. A FURNACE ROOF COMPRISING A PLURALITY OF SPACED PARALLEL MAIN BEAMS EXTENDING ACROSS THE ROOF, A PLURALITY OF CROSS BEAMS TRANSVERSE TO SAID MAIN BEAMS, SAID MAIN BEAMS AND SAID CROSS BEAMS DEFINING A PLURALITY OF RECTANGULAR OPEN FRAMES OF SMALL SIZE COMPARED TO THE SIZE OF THE ROFF AS A WHOLE, EACH OF SAID BEAMS BEING COMPOSED OF SUSPENDED BRICKS, AND FILLER MATERIALS WHICH FILL SAID OPEN FRAMES, SAID FILLER MATERIALS BEING SUPPORTED BY SAID BEAMS. 